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All-Optical Format Conversion of NRZ-OOK to RZ-OOK in a Silicon Nanowire Utilizing Either XPM or FWM and Resulting in a Receiver Sensitivity Gain of

All-optical format conversion of 10 Gb/s non-return-to-zero on-off keying (NRZ-OOK) to RZ-OOK has been successfully achieved, for the first time to our knowledge, utilizing either cross-phase modulation (XPM) or four-wave mixing (FWM), in a Silicon (Si) nanowire. A 10-9-bit-error-rate (BER) receiver sensitivity gain of ~2.8 dB was obtained for converted RZ-OOK relative to NRZ-OOK using XPM, whereas a receiver sensitivity gain of ~2.5 dB was found for the FWM anti-Stokes RZ-OOK. Simultaneous wavelength and pulse format conversions were possible with FWM. No evidence of an error floor for BER <10-10 was observed in either technique. The converted RZ-OOK signal was also correctly encoded and of the correct polarity.

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We have demonstrated for the first time to our knowledge, the conversion of 10 Gb/s non-return-to-zero (NRZ) on-off keying (NRZ-OOK) to RZ-OOK using cross-phase modulation (XPM) in a compact, Silicon (Si) nanowire and a detuned filter. The pulse format conversion resulted in a polarity-preserved, correctly-coded RZ-OOK signal, with no evidence of an error-floor for BER < 10(-11). The advantages of a passive Si nanowire can lead to a compact, power-efficient, highly simplified configuration, amenable to chip-level integration.

2.5 dB

Tunable wavelength conversion of a 10-Gb/s, return-to-zero on-off-keyed (RZ-OOK) signal has been carried out in a silicon (Si) nanowire waveguide (Si nanowire) using a pump-probe configuration and cross-phase modulation (XPM), followed by a tunable filter. This filter spectrally emulated the pass-band of a commercial 50-GHz DWDM arrayed waveguide grating (AWG). The tunability of the wavelength conversion process was demonstrated over a range of 20 nm, limited only by the amplifiers and the filter, while keeping the 10-9-BER receiver sensitivity penalty of the converted signal to a 0.5-dB maximum. A comprehensive model of wavelength conversion by XPM (XPM-WC) was developed, which took into account two-photon absorption, the Kerr effect, and free-carrier generation. The results of the model demonstrate good agreement with the experiment, especially with respect to the observed spectral broadening. The numerical model was also used to assess the dominant contribution among the various mechanisms within the context of XPM-WC, and to investigate the potential of multicasting by XPM in the nanowire.

Conversion of 10 Gb/s NRZ-OOK to RZ-OOK utilizing XPM in a Si nanowire

Wavelength conversion of polarization-scrambled 10-Gb/s on-off keyed and differential phase-shift-keyed signals for which the pulse format was 33% return-to-zero, has been achieved by partially degenerate four-wave mixing in a record 20-m-short highly nonlinear photonic crystal fiber. It was found that a minimum pump-probe detuning of ~9 nm was required to achieve polarization-insensitive wavelength conversion of <1 dB, resulting in a 10-9-receiver sensitivity penalty of <1 dB, for both modulation formats.

Tunable Wavelength Conversion by XPM in a Silicon Nanowire, and the Potential for XPM-Multicasting

Wavelength conversion of a 10 Gb/s 2.7%-duty-cycle return-to-zero (RZ) OOK (RZ-OOK) signal using XPM in a compact silicon nanowire waveguide (Si nanowire) and a detuned filter is successfully demonstrated for the first time. A 10-9-BER receiver sensitivity penalty of <;1 dB was measured for the converted signal relative to the baseline signal, with a filter-probe detuning of 0.6 nm. The system is numerically modeled and the results are shown to match well with the experimental results. The numerical model is further used to design an optimal filter that would eliminate filter-probe detuning.

Erratum to “Polarization-Insensitive Wavelength Conversion by FWM in a Highly Nonlinear PCF of Polarization-Scrambled 10-Gb/s RZ-OOK and RZ-DPSK Signals”

The conversion of data modulation format from 10-Gb/s return-to-zero on-off keying (RZ-OOK) to 10-Gb/s RZ binary phase-shift keying (RZ-BPSK) has been successfully carried out for the first time utilizing cross-phase modulation (XPM) in a passive AlGaAs waveguide. A 10-9-bit-error-rate (BER) preamplified receiver sensitivity gain of ≈ 1 dB was measured for the converted RZ-BPSK relative to baseline RZ-OOK, whereas a penalty of ≈ 2.7 dB relative to baseline RZ-BPSK is explained to be due to cross-absorption modulation induced by nondegenerate two-photon absorption (ND-TPA), as well as to an insufficient nonlinear phase shift.

All-Optical Wavelength Conversion of 10 Gb/s RZ-OOK Data in a Silicon Nanowire via Cross-Phase Modulation: Experiment and Theoretical Investigation

The polarization-insensitive data transfer of 10-Gb/s return-to-zero ON-OFF keying (RZ-OOK) to RZ-binary phase-shift keying (RZ-BPSK) has been successfully carried out for the first time, in a passive birefringent nonlinear Al0.18Ga0.82As waveguide, utilizing polarization-insensitive cross-phase-modulation (PI-XPM). A 10-9 bit-error-rate (BER) pre-amplified receiver sensitivity penalty of ≈2.2 dB relative to baseline RZ-BPSK was measured for PI-XPM, when the RZ-OOK pump was polarization-scrambled and the RZ-probe was launched at 40°. The probes optimal launch angle for PI-XPM was significantly influenced by the anisotropy of the Al0.18Ga0.82As waveguide.

Conversion of RZ-OOK to RZ-BPSK by XPM in a Passive AlGaAs Waveguide

We demonstrate the simultaneous conversion of wavelength and nonreturn-to-zero to return-to-zero (RZ) format at 10 Gb/s, using four-wave mixing in a passive GaAs bulk-waveguide. A conversion efficiency of -28 dB (idler output relative to signal output) and a conversion bandwidth of 48 nm could be achieved in this waveguide, which was fabricated in a single photolithographic step. The conversion efficiency is also characterized and compared with simulated results. The converted RZ on-off keying (RZ-OOK) signal demonstrated a 10-9 bit-error-rate receiver sensitivity penalty of 1 dB relative to baseline RZ-OOK.

Data Transfer From RZ-OOK to RZ-BPSK by Polarization-Insensitive XPM in a Passive Birefringent Nonlinear AlGaAs Waveguide

Polarization-insensitive (PI) phase-transmultiplexing (PTM) of a 10-Gb/s return-to-zero ON-OFF keying (RZ-OOK) pump and a 10-Gb/s RZbinary phase-shift keying (RZ-BPSK) probe to 20-Gb/s RZ-quadrature-PSK (RZ-QPSK) has been successfully demonstrated for the first time in a passive, birefringent AlGaAs waveguide, utilizing PI cross-phase modulation (PI-XPM). For differential QPSK (DQPSK)-detection, a 10 − 9-BER pre-amplified receiver sensitivity penalty of ≈ 2.5 dB for the in-phase component and ≈ 4.9 dB for the quadrature component were found. The penalties were relative to the FPGA-precoded RZ-DQPSK baseline for a pump-probe detuning of ≈ 12 nm, when the probe state of polarization was scrambled and the pump was launched off-axis into the waveguide.

10-Gb/s Wavelength and Pulse Format Conversion Using Four-Wave Mixing in a GaAs Waveguide

By engineering the bandgap to suppress two-photon absorption, we achieve efficient continuous-wave four-wave mixing in a passive AlGaAs waveguide. The observed conversion efficiency (-5.5 dB) is among the highest reported for semiconductor waveguides.